Exclusive: 'NAO' Weather Affects
Europe

The question
is: Is NAO oscillating or not?.

'NAO:' Reason for Milder Than Normal
Spring?

Paris:- Friday, 27. March 1998:- It is no secret
that this magazine has readers who live in California. Less
well-known is that they write about the weather they have
there. No, they do not write about smog.

They have been writing a lot lately about the impossible
behaviour of an infrequent type of winter weather, which
has been given a sensationalist name by the popular press:
it is called 'El Niño.'

Metropole is in the fortunate position of having access
to its own weather experts, or as the British would call
them, 'Boffins,' which I believe is a type of penguin.

Because the California reports are coming in from a wide
area of that large state, I thought it would be reassuring
to readers there to have an expert opinion - so I asked
Mr. Norman
Barth whether residents of Malibu could expect to be
swept out to sea anytime soon; although I'm not aware of
any current readers residing there.

Instead of what I was expecting, Mr. Barth sent
the
surprising and alarming news that Europe has its own
uncharacteristic winter weather system, and it is known by
the slightly less reassuring name of 'NAO.'

France
2's TV-weather looks like a heatwave, but it's only 1/10th
of a degree.

He also suggested I contact David Stephenson in Toulouse
for the true facts about 'NAO' - so that readers readers
intending to visit Europe in order to escape the caprices
of 'El Niño' would not be stricken by panic on
encountering 'NAO' here.

A Rough Guide to the North Atlantic
Oscillation

Toulouse:- Friday, 27. March 1998:- For many of
the past 15 years, a recurring pressure pattern has
resulted in milder than normal winters and springs in
Europe.

After El Niño, this pressure pattern is one of
the most dominant modes of global climate variability, and
is less poetically referred to as the North Atlantic
Oscillation (pronounced en-ay-oh).

In a diary which he kept in Greenland during the years
1770-78, the missionary Hans Egede Saabye made the
following observation: "In Greenland, all winters are
severe, yet they are not alike. The Danes
have noticed that when the winter in Denmark was severe, as
we perceive it, the winter in Greenland in its manner was
mild, and conversely."

This temperature see-saw is now known to be a
manifestation of the NAO.

If in doubt, get an
umbrella at Gely's - on the bd. Saint-Germain, since
1834.

The high index winter/springs of 1989, 1990, and 1995,
were caused by a net displacement of air from over the
Arctic and Icelandic regions towards the subtropic belt
near the Azores and the Iberian peninsula, and had
strengthened westerlies over the North Atlantic ocean.
Stronger westerlies bring more warm moist air over the
European continent and gives rise to milder maritime
winters.

The low index winter/springs of 1917, 1936, 1963, and
1969 had weaker mean westerlies over the North Atlantic
ocean with corresponding colder than normal European
winters.

The strengthened or weakened westerlies over the North
Atlantic are also known to play a major role in controlling
the oceanic ecosystems and ultimately North Atlantic fish
stocks.

After more than 100 years of scientific research, the
fundamental mechanisms behind the variability of the North
Atlantic Oscillation still remain intriguing mysteries.

Some things are however becoming clearer. For example,
it appears that the link between the notorious bad boy of
the tropical Pacific, El Niño, and his nordic
cousin, the NAO, is relatively weak.

It is also becoming clearer that some of the current day
climate models are showing some encouraging ability to make
probabilistic forecasts of the NAO a season ahead.

What is not clear is why the NAO has become more
positive over the last 30 years and there is some
speculation that this may be a sign of human induced global
warming. On the other hand, it could merely be natural
climate variability controlled by the giant dynamo-like
gyres in the North Atlantic ocean.

This question is currently being addressed by analyzing
long simulations of the NAO using state-of-the-art climate
models running on the world's fastest supercomputers.
Because of its climatic importance, the NAO is currently
generating intense scientific interest and this will
undoubtably lead to further advances in our understanding
of this intriguing phenomenon.

What a Relief: No Link
Between El Niño and NAO!

Dr. Stephenson's mention of 'giant dynamo-like gyres in
the North Atlantic' may sound ominous, so I would like to
point out a few fundamentals of European geography.

First off, Toulouse is a lot further away from oceans
than Malibu; but it is sandwiched between the Atlantic and
the Mediterranean - so there is active weather there even
if the city is not in danger of sliding into either body of
water. This applies to Paris as well.

In direct reference to NAO, Denmark is of course in
Europe, but it is way up north, beyond Schleswig-Holstein.
Denmark is a very long way from Greenland and Greenland, as
everybody knows, is about as 'green' as a normal
refrigerator. If you want to worry about Greenland, it is
much closer to Scotland.

The North Atlantic Ocean has specific features not even
found in the Pacific. It has the warm Gulf Stream, part of
which comes from the Caribbean and it picks up more warmth
from Miami, and all of this chugs across the Atlantic and
sprays itself at Europe, except for a bit that drifts up -
beside Scotland! - and along the coast of Norway where it
gets confused in the Arctic Ocean.

Another part of the Gulf Stream pulls clockwise, turning
to
the south around the Azores. Here its name changes to
Canaries Current. The lines on my map go from red to blue
here, even though it is passing a very red spot of Africa.
It keeps going clockwise, gets warmer, and heads west as
the North Equatorial Current. This was Columbus' warm
autobahn to China.

Springtime 'Ile-de-France' sky,
digitally enhanced.

Until quite recently, weather in France was national. If
there was any weather outside France, it was highly
sketchy. In the last couple of weeks, France 2 TV evening
weather has been showing that weather here comes from the
Atlantic, mostly. This is welcome news because we can now
blame it on foreign sources rather than France 2 TV.

Whether it is good or bad, and it is seldom an extreme
of either, it has always been the fault of the so-called
'Azores High.' With this latest information, if the Azores
High does not seem to be at fault, we can blame NAO
instead.

Although this news is of little use to Metropole's
California readers, I would still like to thank Norman
Barth for pointing me towards NAO and Dr. Stephenson for
providing the information about it. For more 'deep
background' about NAO, be sure to check Dr. Stephenson's
Web site, by clicking on his name in the byline.